Responses
He sacrificed himself to give rooster the chance to put yellow dragon to sleep as he was losing control and was gonna destroy everything. Usually the animals spirits would work together to put yellow dragon to sleep while protecting the emperor but since most of animal spirts were destroyed the remaining spirits were not strong enough to do it the regular way.

Omgosh this was just too sad but can someone please reiterate why they needed to die together? I know he transformed into black dragon but I'm still confused why dojin needed to die, he want hurt that badly by that evil witch.
I'M REALLY SORRY THIS WAS PROBS SAID IN THE STORY BUT I'M JUST TOO DUMB TO PIECE IT ALL TOGETHER. SORRY SORRY